U.S. patent number 4,844,039 [Application Number 07/184,353] was granted by the patent office on 1989-07-04 for fuel supply control system for internal combustion engines.
This patent grant is currently assigned to Honda Giken Kogyo K.K.. Invention is credited to Eitetsu Akiyama, Shunzaburo Osaki.
United States Patent |
4,844,039 |
Osaki , et al. |
July 4, 1989 |
Fuel supply control system for internal combustion engines
Abstract
A fuel supply control system for an internal combustion engine
comprises a start detecting device for detecting a starting
condition of the engine, and a starting fuel supply device for
supplying an amount of fuel required for starting the engine which
corresponds to an output generated from a device for detecting an
engine temperature, when the start detecting device detects the
starting condition of the engine. A timer is associated with the
start detecting device for counting time elapsed from the time the
start detecting device detects the starting condition of the engine
and generating an output corresponding to the elapsed time. A fuel
decreasing device is responsive to respective outputs from a
throttle opening sensor and the timer, for decreasing the amount of
fuel for starting the engine, supplied by the starting fuel supply
device.
Inventors: |
Osaki; Shunzaburo (Wako,
JP), Akiyama; Eitetsu (Wako, JP) |
Assignee: |
Honda Giken Kogyo K.K. (Tokyo,
JP)
|
Family
ID: |
16597091 |
Appl.
No.: |
07/184,353 |
Filed: |
April 21, 1988 |
Foreign Application Priority Data
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Aug 25, 1987 [JP] |
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62-210910 |
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Current U.S.
Class: |
123/491;
123/480 |
Current CPC
Class: |
F02D
41/061 (20130101) |
Current International
Class: |
F02D
41/06 (20060101); F02D 041/06 () |
Field of
Search: |
;123/491,480,486,179L,179G ;364/431.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nelli; Raymond A.
Attorney, Agent or Firm: Lessler; Arthur L.
Claims
What is claimed is:
1. In a fuel supply control system for an internal combustion
engine having an intake passage and a throttle valve arranged
across said intake passage, including
start detecting means for detecting a starting condition of said
engine,
engine temperature detecting means for detecting a temperature of
said engine and generating an output indicative of the detected
engine temperature,
throttle opening detecting means for detecting the opening degree
of said throttle valve and generating an output indicative of the
detected opening degree, and
fuel supply means associated with said start detecting means and
said engine temperature detecting means and responsive to said
output of said engine temperature detecting means, for supplying
said engine with an amount of fuel required for starting said
engine, when said start detecting means detects said starting
condition of said engine,
the improvement comprising:
time counting means associated with said start detecting means for
counting time elapsed from the time said start detecting means
detects said starting condition of said engine and generating an
output depending upon whether or not said elapsed time is larger
than a predetermined period of time, said predetermined period of
time being determined by said output of said throttle opening
detecting means, and
fuel decreasing means responsive to said output of said time
counting means, for decreasing said amount of fuel for starting
said engine, to be supplied by said fuel supply means, after said
predetermined period of time has elapsed.
2. A fuel supply control system as claimed in claim 1, wherein said
fuel decreasing means decreases said amount of fuel for starting
said engine, when the opening degree of said throttle valve
detected by said throttle opening detecting means is smaller than a
predetermined value, and at the same time said elapsed time counted
by said time counting means is larger than said predetermined time
period.
3. A fuel supply control system as claimed in claim 1, wherein said
fuel decreasing means decreases said amount of fuel for starting
said engine, when the opening degree of said throttle valve
detected by said throttle opening detecting means is larger than a
predetermined value, and at the same time said elapsed time counted
by said time counting means is larger than said predetermined
period of time.
4. A fuel supply control system as claimed in claim 3, wherein said
fuel decreasing means decreases said amount of fuel for starting
said engine, when the opening degree of said throttle valve
detected by said throttle opening detecting means is smaller than
said predetermined value, and at the same time said elapsed time
counted by said time counting means is larger than a second
predetermined period of time which is longer than said
first-mentioned predetermined period of time.
5. A fuel supply control system as claimed in claim 1, wherein said
fuel decreasing means inhibits said decreasing of said amount of
fuel for starting said engine when the temperature of said engine
detected by said engine temperature detecting means is higher than
a predetermined value, and allows said decreasing of said amount of
fuel for starting said engine when the detected engine temperature
is lower than said predetermined value.
6. A fuel supply control system as claimed in any one of claims 1
to 5, wherein said amount of fuel for starting said engine is a
basic value corresponding to the detected engine temperature, said
fuel decreasing means decreasing said amount of fuel for starting
said engine by multiplying said basic value by a correction
coefficient.
Description
BACKGROUND OF THE INVENTION
This invention relates to a fuel supply control system for an
internal combustion engine, and more particularly to such a control
system, which can properly control a fuel quantity to be supplied
to the engine at the start of the engine.
Fuel supply control systems for an internal combustion engine are
known e.g. from Japanese Patent Publications No. 57-27972 and
60-29824, in which excessive enrichment of an air/fuel mixture to
be supplied to the engine at starting, and smoldering of ignition
plugs which are wetted with fuel due to the excessive enrichment,
are prevented in order to improve the startability of the
engine.
According to the Japanese Patent Publication No. 57-27972, the
opening of a throttle valve in the intake passage of the engine is
detected at the start of the engine, and fuel supply to the engine
is reduced or cut off immediately upon detection of the opening
motion of the throttle valve from a closed position to an open
position. However, if the driver already depresses the accelerator
pedal just before the start of the engine so that the throttle
valve is already open at the start of the engine, or if the
throttle valve is erroneously detected to be already open at the
start of the engine due to the malfunction of a throttle opening
sensor, fuel supply is immediately reduced or cut off immediately
upon turning on the starter, and consequently a quantity of fuel
sufficient for causing firing within combustion chambers cannot be
supplied, resulting in failure to start the engine.
According to the Japanese Patent Publication No. 60-29824, a fuel
quantity to be supplied to the engine at starting is controlled to
be gradually reduced in accordance with the number of crank angle
pulses generated from the start of the engine. However, according
to this method, it takes much time until the fuel quantity is
sufficiently reduced. As a result, an enriched air/fuel mixture is
supplied to the engine for a long time after the start of the
engine, so that ignition plugs continue to smolder, resulting in
failure to start the engine.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a fuel supply control
system for internal combustion engines, which is capable of
preventing the engine from failing to start, and promptly removing
the smoldering of ignition plugs, if it occurs, thereby improving
the startability of the engine.
According to the present invention, there is provided a fuel supply
control system for an internal combustion engine having an intake
passage and a throttle valve arranged across the intake passage,
including start detecting means for detecting a starting condition
of the engine, engine temperature detecting means for detecting a
temperature of the engine and generating an output indicative of
the detected engine temperature, throttle opening detecting means
for detecting the opening degree of the throttle valve and
generating an output indicative of the detected opening degree, and
starting fuel supply means associated with the start detecting
means and the engine coolant temperature detecting means and
responsive to the output of the engine temperature detecting means,
for supplying the engine with an amount of fuel required for
starting the engine, when the start detecting means detects the
starting condition of the engine.
The fuel supply control system according to the invention is
characterized by the improvement comprising: time counting means
associated with the start detecting means for counting time elapsed
from the time the start detecting means detects the starting
condition of the engine and generating an output corresponding to
the elapsed time, and fuel decreasing means responsive to the
outputs of the throttle opening detecting means and the time
counting means, for decreasing the amount of fuel for starting the
engine, supplied by the starting fuel supply means.
The invention will be more apparent from the ensuing detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating the whole arrangement of a
fuel supply control system of an internal combustion engine
according to the invention;
FIG. 2 is a block diagram illustrating the interior arrangement of
an electronic control unit (ECU) 5 appearing in FIG. 1;
FIG. 3 is a graph showing a table of the relationship between a
basic valve opening period Ti.sub.CR of fuel injection valves 6 at
cranking of the engine and the engine coolant temperature T.sub.W ;
and
FIG. 4 is a flow chart showing a manner of determining the basic
valve opening period correction coefficient K.sub.CR of the fuel
injection valves 6 at cranking of the engine.
DETAILED DESCRIPTION
The invention will now be described in detail with reference to the
drawings showing an embodiment thereof.
Referring first to FIG. 1, there is illustrated the whole
arrangement of a fuel supply control system of an internal
combustion engine according to the invention. In the figure,
reference numeral 1 designates an internal combustion engine which
may be a four-cylinder type for instance, and to which is connected
an intake pipe 2 forming an intake passage. A throttle body 3 is
arranged across the intake pipe 2, and accommodates a throttle
valve 3'. A throttle valve opening (.theta..sub.TH) sensor 4 is
connected to the throttle valve 3' for sensing its valve opening
and is electrically connected to an electronic control unit
(hereinafter called "the ECU") 5, to supply same with an electrical
signal indicative of the throttle valve opening sensed thereby.
Fuel injection valves 6 (starting fuel supply means) are arranged
in the intake pipe 2 each at a location slightly upstream of an
intake valve, not shown, of a corresponding one of the engine
cylinders, not shown, and between the engine 1 and the throttle
body 3, for supplying fuel to the corresponding engine cylinder.
The fuel injection valves 6 are connected to a fuel pump, not
shown, to be supplied with pressurized fuel therefrom and are
electrically connected to the ECU 5, in a manner having their valve
opening periods of fuel injection quantities controlled by signals
supplied from the ECU 5.
An absolute pressure (P.sub.BA) sensor 8 communicates through a
conduit 7 with the interior of the intake pipe 2 at a location
downstream of the throttle valve 3' of the throttle body 3, to
sense absolute pressure in the intake pipe 2 and applies an
electrical signal indicative of sensed absolute pressure to the ECU
5.
An engine coolant temperature (T.sub.W) sensor 9, which may be
formed of a thermistor or the like, is mounted on the cylinder
block of the engine 1 in a manner embedded in the peripheral wall
of an engine cylinder having its interior filled with coolant, of
which an electrical output signal indicative of the sensed coolant
temperature is supplied to the ECU 5.
An engine speed (Ne) sensor 10 is arranged on a camshaft, not
shown, of the engine 1 or a crankshaft of same, not shown. The Ne
sensor 10 is adapted to generate one pulse at one of predetermined
crank angles whenever the engine crankshaft rotates through 180
degree, i.e. one pulse of the top-dead-center position (TDC)
signal. The pulses generated by the sensor 10 are supplied to the
ECU 5.
The engine 1 is provided with a starter 11, which drives the engine
1 at cranking or starting. The starter 11 is connected to the ECU 5
via a starter switch 11a which supplies a signal indicative of
on-off state of the starter to the ECU 5. The starter switch 11a is
constructed as start detecting means together with a central
processing unit 503, a level shifter 512, and a data circuit 513,
hereinafter referred to.
Further connected to the ECU 5 are other engine operating parameter
sensors 12 such as an intake air temperature sensor, an atmospheric
pressure sensor, an O.sub.2 sensor, and so forth, which supply
respective output signals indicative of the sensed parameter values
to the ECU 5.
The ECU 5 determines engine operating conditions, based upon the
input signals from the above-mentioned various engine operating
parameter sensors, and calculates fuel quantity to be supplied to
the engine 1, that is, the valve opening period T.sub.OUT for the
fuel injection valves 6 in response to the determined conditions of
the engine 1.
The valve opening period T.sub.OUT for the fuel injection valves 6
at cranking of the engine can be obtained by the use of the
following equation (1):
where Ti.sub.CR is a basic valve opening period for the fuel
injection valves 6 to be applied at the start of the engine 1 in
dependence on the engine coolant temperature T.sub.W. The value of
the basic valve opening period Ti.sub.CR is determined, for
instance, by means of a Ti.sub.CR table in FIG. 3. In the Ti.sub.CR
table, five predetermined values Ti.sub.CR1 -Ti.sub.CR5 of the
basic valve opening period Ti.sub.CR and five predetermined values
TW.sub.CR1 -TW.sub.CR5 of the engine coolant temperature T.sub.W
are provided as calibration variables dependent upon the engine
coolant temperature T.sub.W. If the detected engine coolant
temperature T.sub.W value falls between adjacent ones of the
predetermined values TW.sub.CR1 -TW.sub.CR5, the basic valve
opening period Ti.sub.CR is calculated by an interpolation
method.
K.sub.CR is a basic valve opening period correction coefficient
according to the present invention which is determined by means of
a control program shown in FIG. 4, hereinafter referred to.
K.sub.Ne is a correction coefficient which is determined in
response to engine rotational speed. T.sub.V is a correction
variable which is determined in response to the output voltage of a
battery, not shown, for supplying electric power to the ECU 5,
etc.
FIG. 2 shows a circuit configuration within the ECU 5 in FIG. 1. An
output signal from the Ne sensor 10 in FIG. 1 indicative of the
rotational speed of the engine is applied to a waveform shaper 501,
wherein it has its pulse waveform shaped, and supplied as the TDC
signal to a central processing unit (hereinafter called "the CPU")
503. The CPU is constructed as fuel decreasing means in the present
embodiment. The TDC signal is supplied to an Me value counter 502,
as well. The Me value counter 502 counts the interval of time
between a preceding pulse of the TDC signal and a present pulse of
the same signal, inputted thereto from the Ne sensor 10. Therefore,
its counted value Me corresponds to the reciprocal of the actual
engine rotational speed Ne. The Me value counter 502 supplies the
counted value Me to the CPU 502 via a data bus 510.
Respective output signals from the throttle valve opening
(.theta..sub.TH) sensor 4, the absolute pressure (P.sub.BA) sensor
8, the engine coolant temperature (T.sub.W) sensor 9, all appearing
in FIG. 1, and other sensors have their voltage levels shifted to a
predetermined voltage level by a level shifter circuit 504 and
successively applied to an analog-to-digital converter 506 through
a multiplexer 505. The analog-to-digital converter 506 successively
converts into digital signals analog output voltages from the
aforementioned various sensors, and the resulting digital signals
are supplied to the CPU 503 via the data bus 510.
The on-off state signal from the starter switch 11a in FIG. 1 has
its voltage level shifted to a predetermined voltage level by a
level shifter 512 and, after being converted into a predetermined
signal in a data input circuit 513, is supplied to the CPU 503 via
the data bus 510.
A T.sub.CR timer 511 as time-measuring means is connected to the
CPU 503. The CPU 503 supplies the T.sub.CR timer 511 with a signal
which causes same to be actuated or stopped, while the T.sub.CR
timer 511 supplies the CPU 503 with a signal indicative of the
counted value thereof.
Further connected to the CPU 503 via the data bus 510 are a
read-only memory (hereinafter called "the ROM") 507, a random
access memory (hereinafter called "the RAM") 508 and a driving
circuit 509. The RAM 508 temporarily stores various calculated
values from the CPU 503, while the ROM 507 stores the
aforementioned Ti.sub.CR table, as well as control programs to be
executed within the CPU 503, such as one in FIG. 4 hereinafter
referred to, and so on. The CPU 503 executes a fuel supply control
program stored in the ROM 507 to calculate the fuel injection
period T.sub.OUT for the fuel injection valves 6 in response to the
various engine operating parameter signals, and supplies the
calculated period value to the driving circuit 509 through the data
bus 510. The driving circuit 509 supplies driving signals
corresponding to the above calculated T.sub.OUT value to the fuel
injection valves 6 to drive same.
Referring to FIG. 4, the control program is shown therein which
determines the aforementioned basic valve opening period correction
coefficient K.sub.CR (hereinafter called "coefficient K.sub.CR ")
according to the present invention, which is executed by the CPU
503 in FIG. 2 in synchronism with generation of the TDC signal,
i.e. whenever each pulse of the TDC signal is inputted to the CPU
503.
First, when the present loop is the first loop after the starter
switch 11a is turned on, the T.sub.CR timer 511 is started by the
signal from the CPU 503 (step 401). The T.sub.CR timer 511 is
adapted to count clock pulses corresponding to elapsed time after
the engine 1 starts to operate.
Next, it is determined whether or not the value of the engine
coolant temperature T.sub.W is smaller than a predetermined value
T.sub.WCRR (e.g. 105.degree. c) at step 402. If the answer to the
question if No, that is, if T.sub.W .gtoreq.T.sub.WCRR, which means
the engine coolant temperature T.sub.W is extremely high, the
counted value T.sub.CR of the T.sub.CR timer 511 which has been
started at step 401 is reset to zero at step 403, since at such a
high temperature the degree of atomization of fuel would be so high
that there occurs no smoldering of ignition plugs. Then, at step
404, the value of the coefficient K.sub.CR is set to a value of
1.0, which is followed by termination of the program. Thus, in this
case, the basic valve opening period Ti.sub.CR is not corrected
actually.
If the answer to the question of the step 402 is Yes, that is, if
T.sub.W <T.sub.WCRR, it is determined whether or not the starter
switch 11a is in on-state at step 405. If the answer to the
question of the step 405 is No, that is, if the switch 11a is not
in on-state, the steps 403 and 404 are executed, followed by
termination of the program, since it is judged that the engine 1 is
no longer cranking or starting.
If the answer to the question of the step 405 is Yes, that is, if
the starter switch 11a is in on-state, it is determined whether or
not the throttle valve opening .theta..sub.TH is larger than a
predetermined value .theta..sub.THCRR (e.g. 70.degree. C.) at step
406. If the answer to the question of the step 406 is yes, that is
if .theta..sub.TH >.theta..sub.THCRR, which means the throttle
valve 3' is sufficiently opened, it is determined whether or not
the counted value T.sub.CR of the T.sub.CR timer 511 is larger than
a value corresponding to a second predetermined period of time
T.sub.CRR1 (e.g. 1.0 sec) at step 407. If the answer to the
question of the step 407 is No, that is, if the second
predetermined period of time T.sub.CRR1 has not yet elapsed from
the start of the engine 1, the step 404 is executed to set the
coefficient K.sub.CR to 1.0, which means the basic valve opening
period Ti.sub.CR is not corrected actually. On the other hand, if
the answer to the question of the step 407 is Yes, that is, if the
second predetermined period of time T.sub.CRR1 has elapsed from the
start of the engine 1, the value of the coefficient K.sub.CR is set
to a predetermined value K.sub.CR1 smaller than the value of 1.0,
e.g. 0.2, at step 408, followed by the excecution of correcting the
basic valve opening period Ti.sub.CR by means of the predetermined
value K.sub.CR1 to which the coefficient K.sub.CR has been set,
which is followed by termination of the program.
As described above, even if the throttle valve 3' is already
sufficiently open at the start of the engine 1, correction of the
quantity of fuel to a reduced value by means of the coefficient
K.sub.CR is not executed, until at least the second predetermined
period of time T.sub.CRR1 elapses from the start of the engine 1.
Therefore, even if the driver already depresses the accelerator
pedal just before turning the starter 11 on or steps on the pedal
simultaneously upon turning the starter 11 on, or even if there
occurs malfunction in the .theta..sub.TH sensor 4, the fuel
quantity at least sufficient for firing within combustion chambers
is supplied to the engine 1, thereby preventing the failure to
start the engine 1. Further, since the fuel quantity reducing
correction by means of the coefficient K.sub.CR is executed
immediately after the second predetermined period of time
T.sub.CRR1 elapses from the start of the engine 1, smoldering of
ignition plugs can be prevented, or the smoldering of ignition
plugs, if it occurs, can be promptly removed.
If the answer to the question of the step 406 is No, that is, if
.theta..sub.TH .ltoreq..theta..sub.THCRR, which means the throttle
valve 3' is not sufficiently opened, it is determined at step 409
whether or not the counted value T.sub.CR of the T.sub.CR timer 511
is larger than a value corresponding to a first predetermined
period of time T.sub.CRRO (e.g. 10.0 sec) which is larger than the
second predetermined period of time T.sub.CRR1. If the answer to
the question of the step 409 is No, that is, if T.sub.CR
.ltoreq.T.sub.CRRO, the step 404 is executed, while if the answer
is Yes, that is, if T.sub.CR >T.sub.CRRO, the step 408 is
executed.
In automotive vehicles in general, to start the engine, the drivers
normally continue cranking operation for about 15 seconds if the
throttle valve 3' is kept closed. However, when the cranking
operation is continued for more than about 10 seconds, the ignition
plugs can smolder. Therefore, the above-mentioned first
predetermined time period T.sub.CRRO is set to a time period before
which the ignition plugs cannot smolder.
If the engine is not brought into a self-sustained operative state,
i.e. a firing or idling state even after the starting operation
described as above, or after repeating the starting operation,
usually the throttle valve 3' will be opened above the
predetermined opening .theta..sub.THCRR by the driver in order to
again try to start the engine so that the correction of the fuel
quantity will be executed by means of the coefficient K.sub.CR at
step 408 after the lapse of the short second predetermined time
period T.sub.CRR1, thereby promptly removing the smoldering of the
ignition plugs and hence improving the startability of the
engine.
* * * * *